A wind turbine transfers the energy of the wind into electrical energy. The wind turbine comprises a nacelle that is connected to a tower, and a rotor that is connected to the nacelle. The nacelle is usually enclosed by a housing.
The rotor comprises a hub that is rotatably mounted to the nacelle and at least one rotor blade mounted to the hub.
The wind interacts with the rotor blade of the wind turbine in a way that the rotor rotates. The rotation of the rotor is transferred to an electrical generator. The electrical generator is normally a part of the nacelle.
When the wind turbine is erected, the tower is set up and the nacelle is mounted onto the tower. The hub is mounted to the nacelle and the at least one rotor blade is mounted to the hub.
The at least one rotor blade is hoisted up by a crane and connected to the hub. The hub has to be in a predetermined angular rotational position around its axis of rotation to establish the connection between the hub and the rotor blade.
This position corresponds to the direction of the blade during the fastening of the connection. The position can be a horizontal or a vertical arrangement of the hub and the rotor blade for example.
The hub has to be rotated to establish the connection between the hub and a first rotor blade. In the case of more than one rotor blade that has to be mounted, the position of the hub has to be changed. The hub has to be rotated form the first rotational position into a second position to establish the connection between the hub and the second rotor blade.
EP 1 659 286 A1 describes a turning device to rotate the drive train of a wind turbine. The drive train is rotatably mounted in a machine frame. The drive train comprises a flange and the arrangement to rotate the drive train comprises a bracket, which can be fixed to a machine frame. An adapter disk can be affixed to the flange and has a plurality of force application points which are disposed along a circle. A linear setting element is, on the one hand, mounted movably in terms of angle in the bracket. It can, on the other hand, be coupled movably in terms of angle to the adaptor disk by way of the force application points thereof.
The turning device is installed in the nacelle of the wind turbine for the installation of the rotor blades or when a rotation of the hub is needed for service. After the installation of the rotor blades the turning device is dismantled from the wind turbine.
After the installation a first rotor blade, the mass of the rotor blade acts with a certain lever on the hub. Thus a powerful drive is needed to turn the rotor in the position for the installation of a second rotor blade.
This shows the disadvantage that the linear actuator needs to be very strong to turn the rotor of the wind turbine.